Recently, high-order emission control has been applied to diesel engines (hereinafter simply referred to as engine). Accordingly, it has been desired to mount an exhaust gas purifier to purify atmospheric pollutants contained in exhaust gas on a working machine such as a construction civil-engineering machine, an agricultural machine, and an engine generator on which an engine is mounted. As an exhaust gas purifier, a diesel particulate filter (hereinafter referred to as DPF) to collect particulate matter and such substances contained in exhaust gas has been known (see patent documents 1 to 3).